This retrospective study aimed to assess the value of a real-time, ultrasound-guided biopsy in evaluating internal mammary lymph nodes (IMLNs) in breast cancer.Patients who were diagnosed with breast cancer and underwent real-time, ultrasound-guided core-needle biopsy (CNB) or fine-needle aspiration (FNA) in suspected IMLN metastasis were retrospectively analyzed. Patient information and ultrasonographic images were reviewed and correlated with pathology results.Of the 164 IMLNs that were subjected to CNB, 131 were positive for metastasis by histopathologic confirmation, 8 were negative, and 25 were insufficient. By FNA, 84 IMLNs were regarded as positive for metastasis, 4 were negative, and 4 were insufficient. In total, there were 215 (83.98%) metastatic IMLNs, 12 benign IMLNs, and 29 unconfirmed by histopathology. There were statistically significant differences in the success of puncture sampling and detection of IMLN metastasis between the CNB and FNA groups (P < .05). There were no significant complications reported after FNA or CNB, including bleeding, nerve injury, infection, pneumothorax, or hemothorax.Our study showed that ultrasonography accurately detected nodes that were likely to be malignant IMLNs, and that real-time, ultrasound-guided CNB and FNA are accurate and valuable techniques for the determination of status in breast cancer patients. Moreover, performing ultrasound-guided CNB and FNA on suspicious IMLN metastasis does not have additional severe complications.Copyright © 2021. Published by Elsevier Inc.